1. Field
One embodiment of the invention relates to an image display apparatus and an image display method which display images by illuminating a liquid-crystal panel with backlighting.
2. Description of the Related Art
In recent years, liquid-crystal display devices have been used as image display means for television sets, personal computers, mobile phones, and the like. A liquid-crystal display device is composed of a liquid-crystal panel and a backlight provided on the rear of the liquid-crystal panel. Since the liquid-crystal panel emits no light, the backlight illuminates the liquid-crystal panel, thereby displaying an image.
Recently, there has been a strong demand toward an improvement in the quality of images displayed by the liquid-crystal display device and various techniques have been proposed. A liquid-crystal display device has been proposed which displays high-quality images with less energy by using the technique for separately controlling light sources (LEDs) constituting a backlight. As an example, Jpn. Pat. Appln. KOKAI Publication No. 2002-99250 (document 1) has disclosed a display apparatus which controls the luminance of each illumination region of the illumination unit on the basis of an input image signal. As another example, Jpn. Pat. Appln. KOKAI Publication No. 2007-219125 (document 2) has disclosed an electro-optical apparatus which detects the illuminance of ambient environment light and switches between the transmissive display mode and the reflective display mode according to the illuminance of the environment light.
As described above, various image quality improvement techniques have been proposed, but there is no end to demands for image quality improvement.
For example, the display apparatus disclosed in document 1 controls the luminance of each illumination region without taking the illuminance of the surroundings into account. Accordingly, in dark surroundings, the displayed image may be too bright or have too high a contrast. Conversely, in bright surroundings, the displayed image may be too dark or have too low a contrast. In addition, the display apparatus disclosed in document 1 controls the luminance of each illumination region without taking the attribute of the input image signal into account. Accordingly, for example, when an image based on the input image signal into which a film image has been converted is displayed, the displayed image is too bright or has too high a contrast, which makes it difficult to display the film image suitably.
Furthermore, the electro-optical apparatus disclosed in document 2 switches between the transmissive display mode and the reflective display mode according to the illuminance of the surroundings without taking the characteristic of the displayed image into account, which makes it difficult to display an image suitably.